<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        #grey{
            background-color: grey;
            width: 800px;
            height: 800px;
        }
        #container{
            background-color: yellow;
            width: 100px;
            height: 100px;
            display: flex;
            justify-content: center;
       
        }
        #one{
            background-color: blue;
            height: 30px;
            width: 30px;
            border-radius: 50%;
            align-items: flex-start;
        }
        #two{
            background-color: blue;
            height: 30px;
            width: 30px;
            border-radius: 50%;
           align-self: center;
        }
        #three{
            background-color: blue;
            height: 30px;
            width: 30px;
            border-radius: 50%;
            align-self: flex-end;
        }
    </style>
</head>
<body>

    <div id="container">
        <div id="one"></div>
        <div id="two"></div>
        <div id="three"></div>
    </div>
</body>
</html>